The specific embodiment of the invention as disclosed herein is provided for use with a selective formation tester apparatus of the kind disclosed in the Hallmark applications Ser. No. 146,706, Filed May 5, 1980, now U.S. Pat. No. 4,246,782 and Ser. No. 146,681, Filed May 5, 1980 now U.S. Pat. No. 4,248,081. Consequently, these disclosures are specifically incorporated herein by reference and the construction and operation of the selective formation tester apparatus disclosed in these referenced applications will differ in the following description only to the extent as modified to utilize the present invention.
The present invention is an improvement to the apparatus disclosed in the incorporated references in that it enables such tester apparatus to be used in testing earth formations in well bores after well casing has been cemented into place.
A valuable capability of the present invention is to permit the owner or operator of a well which may have been previously completed to produce oil or gas from a particular zone of formation, to subsequently test other potentially productive zones through the well casing. There are a great many wells which were initially completed to produce a zone which subsequently has become too depleted for economic production. In such wells having one or more other zones which are potentially productive, the productive life of that well may be renewed by testing such zones with the present invention and recompleting the well to produce from a more productive zone.